Adjustable clutch construction

ABSTRACT

A portable power tool including a housing having an integral handle. A motor within the housing imparts rotation or longitudinal percussion or both to a tool bit which is engageable with a work surface. A novel adjustable friction clutch forming part of a drive train which transmits rotation to the bit, interconnects two shafts to transmit rotary movement therebetween but allows one shaft to slip relative to the other such as when the bit becomes frozen in the work.

United States Patent inventors Leo A. McCafferty, Jr.

Baltimore;

Robert G. Moores, Jr., Towson, both of, Md.

Aug. 19, 1969 June 22, 1971 The Black and Decker Manufacturing CompanyTowson, Md.

Appl. No. Filed Patented Assignee ADJUSTABLE CLUTCH CONSTRUCTION 12Claims, 6 Drawing Figs.

US. Cl 64/30C, 81/524, 151/415, 173/12, 173/109, 267/177 Int. Cl Fl6d7/02, F161: 39/28 Field of Search 64/29, 30

[56] References Cited UNITED STATES PATENTS 1,138,179 5/1915 Bayles151/415 (X) 1,451,999 4/1923 Perry.... 151/4l.5 (X) 1,463,497 7/1923Bugatti. 81/52.4 1,488,069 3/1924 Seago 151/415 (X) 1,874,888 8/1932Burrell 81/52.4 (UX) 2,430,606 1 1/1947 Franz 151/41.5 2,654,407 10/1953Dremel..... 81/524 (X) 2,716,875 9/1955 Hill et a1. 64/29 3,396,557 8/1968 Moores, Jr 64/30 Primary Examiner-Allan D. Hermann Att0rneysLeonardBloom and Joseph R. Slotnik ABSTRACT: A portable power tool including ahousing having an integral handle. A motor within the housing impartsrotation or longitudinal percussion or both to a tool bit which isengageable with a work surface. A novel adjustable friction clutchforming part of a drive train which transmits rotation to the bit,interconnects two shafts to transmit rotary movement therebetween butallows one shaft to slip relative to the other such as when the bitbecomes frozen in the work.

PATENTEDJUN22|97| 3585.817

INVENTORS ROBERT G. 00R 8 JR. WQW

ATTORNEY LEO A. MC CAFFERTY, JR.

ADJUSTABLE CLUTCH CONSTRUCTION SUMMARY OF THE INVENTION This inventionis directed to a novel rotary slip clutch construction having input andoutput members. Frictional force is developed within the clutch by aresilient member acting on friction members connected to the clutchinput and output members. The torque level at which slip occurs isreadily adjustable through a member acting in the resilient member. Theresilient member has means integrated therewith which acts on theadjustment member to retain it in its adjusted position and preventsunintended adjustment thereof.

Main objects of the present invention, therefore, are to provide a noveladjustable rotary slip clutch construction which facilitates readyadjustment of the torque level at which slip will occur but preventsunintended or accidental adjustment thereof.

Another important object of this invention is to provide a novel slipclutch construction of the above character which includes a minimum ofseparate parts and is compact and light in weight.

Additional objects are to provide a novel construction of the abovecharacter which is relatively inexpensive to manufacture, rugged inconstruction, and reliable in use.

Further objects and advantages of the invention will become moreapparent with a consideration of the detailed description to followtaken in conjunction with the claims annexed hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational viewillustrating a power tool embodying the present invention;

FIG. 2 is an enlarged sectional view of a portion of FIG. 1 illustratingthe clutch of the present invention;

FIG. 3 is an exploded perspective view of some of the clutch parts ofFIG. 2;

FIG. 4 is a view similar to FIG. 2 but illustrating the clutch parts inanother adjusted position;

FIG. 5 is a sectional view of FIG. 2 taken along the line 5-5 thereof;and

FIG. 6 is a sectional view of FIG. 2 taken along the line 6-6 thereof.

BROAD STATEMENT OF THE INVENTION Broadly described, the presentinvention relates to a portable power tool of the type having a tool bitsupported for rotation and longitudinal reciprocation, said tool havinga transmission including a rotary slip clutch adapted to transmit rotarymotion to said tool bit below a preselected torque level; theimprovement in said tool wherein said clutch comprises input and outputmembers, engageable first and second friction means connected to saidinput and output members, respectively, a coil spring normally biasingsaid first and second friction means into operative frictionalengagement, adjustment means holding said resilient means in its biasingposition and movable in directions toward and away from said resilientmeans to effect adjustment of the biasing force of said resilient meanson said first and second friction means, said coil spring having anopening in one end thereof, and detent means including a ball partiallydisposed in said opening and cooperably receivable in recess means insaid adjustment means to resist said movement of said adjustment means,whereby the biasing force of said resilient means inhibits said movementof said adjustment means.

In another aspect, the present invention relates to a rotary frictionclutch comprising generally concentric rotary input and output members,first and second frictional plate means fixed for rotation with saidinput and output members, respectively, a compression spring biasingsaid first and second friction plate means into operative frictionalengagement, a cage member threaded to said input member and holding saidcompression spring in biasing relation to said friction plate means andadapted when threaded along said input member to vary the biasing forceof said spring on said friction plate means, detent means including aball partially received in an opening formed in one end coil of saidspring, said cage member having at least one pocket adapted tocooperably receive said ball, whereby to releasably hold said cagemember against turning movement relative to said input member.

DETAILED DESCRIPTION Referring now more specifically to the drawings, anelectric powered, rotary hammer embodying the present invention isillustrated generally at 11 in FIG. I; however, this tool is forpurposes of illustration only and it is to be understood that thepresent invention finds more general use in the field of power drivenrotary tools and particularly those which are subject to high impactforces during use.

With this in mind, the tool 11 is seen to include a case housing 13having an end housing 15 secured thereto by screws 17. An end handle andgear case 19 is fixed to the case housing 13 by screws 21. The handleand gear case 19 has a trigger switch 23 and a conventional line cord 25supported thereon.

The rotary hammer I1 is provided with a conventional electric motor (notshown) or other power source which may be positioned within the lowerportion of the case housing 13 and which is adapted to impartlongitudinal reciprocation and rotation to a tool bit 27. To reciprocatethe tool bit 27, the motor (not shown) may have a rotating armatureconnected to a piston and floating ramby a gear and crank transmissionso that the ram is reciprocated and hammers on the tool bit 27. One suchconstruction is illustrated and described in detail in U. S. Pat. No.3,203,490, granted Aug. 31, 1965, to G. W. McCarty et al., and owned bythe assignee of the present application, and reference may be madethereto for a better understanding thereof.

A tool retainer plate 29 is carried upon the end housing 15 and iscentrally apertured to rotatably and slidably receive a reduced diameterportion 30 of the tool bit 27. The retainer plate 29 is resilientlymounted on the end housing and prevents the tool bit 27 from pulling outofthe end housing 15. For a detailed description of the mounting of theretainer plate 29, reference may be made to the US. Pat. to Moores, No.3,454,284, granted July 8, 1969, and owner by the assignee of thepresent application.

As described above, the tool bit is adapted for rotation about itslongitudinal axis as well as reciprocation therealong. To this end, theelectric motor armature (not shown) has a shaft (not shown) drivinglyinterconnected to an input shaft 31 of a novel rotary slip clutch 33(see FIG. 2). A hollow clutch output shaft 36 is concentric with theinput shaft 31 and imparts rotation to the bit 27 through a gear train(not shown). Preferably, but not necessarily, the tool bit 27 has ahexagonal or splined shank slidably received in a complementary openingin a gear, the former being illustrated and described in the aforesaidMcCarty et al. patent.

The slip clutch 33 is employed to prevent excessive reaction torque frombeing imparted to the operator. Thus, for example, when the bit 27becomes frozen in a workpiece and cannot turn, the clutch 33 slips andprevents injury to the operator or damage to the tool.

As shown in FIG. 2, the slip clutch 33 includes a first set of plates 35each having a noncircular opening 37 nonrotatably disposed on acomplementary shaped portion 39 of the clutch input shaft 31. Arrangedbetween adjacent ones of the plates 35 are respective ones of a secondset of plates 41 having large openings 42 loosely disposed on the shaftportion 39. Each of the second plates 41 is keyed to a clutch housing 43by radially projecting cars 45 on the plates 41 which are received inaxial grooves 47 in the housing 43. The clutch housing 43 has a boss 49threaded on the output shaft 36 so that the first set of plates 35rotates with input shaft 31 while the second set of plates 41 rotateswith the output shaft 36.

The plates 35, M are biased into operative frictional engagement by acoil compression spring 53 caged between the plates 35, 41 and a clutchcover 55 threaded on a reduced end 57 of the shaft 31. The plates 35,411 may either directly engage in face-to-face relation, or they mayoperatively engage through spacer friction plates 51 which are looselydisposed upon the shaft portion and within the housing 43. The cover 55is disposed wholly outside the end housing and has a counterboredportion 59 piloted on a pilot portion 61 of the shaft 31 for stability.Thus, when it is desired to adjust the torque level at which the clutch33 slips, the cover 55 is manually turned on the shaft 31 and isthreaded up or back on the shaft end 57 depending on whether it isdesired to raise or lower this torque level.

It will be appreciated that vibratory forces arise in the tool 11 duringuse. These forces tend to turn the clutch cover 55 thereby changing thetorque level adjustment. ln order to prevent this from occurring, novelmeans is provided on the spring 53 which prevents the clutch cover 55from inadvertently or accidentally turning but which allows the clutchcover 55 to be easily adjusted when desired.

As shown in FIGS. 2-4, the spring 53 has a ball 63, constructed ofhardened steel or other similarly durable material, seated in an opening65 in its outermost coil. The ball 63 projects outwardly of this coil,preferably a distance of about ($41) to about A) the ball diameter andis adapted to seat selectively in one of a plurality of generallycomplementary pockets 67 formed in a radial face of the clutch cover 55.Similarly, another ball 69 is seated in an opening 71 in the innermostspring coil 73. Like the ball 63, the ball 69 projects about ('A) toabout 1%) the ball diameter from the opening 71 and seats selectively inone of a plurality of recesses 75 formed in the adjacent face of theclutch plate 35.

It will be appreciated that the balls 63, 69 are biased into seatedrelation with the recesses 67, 75 by the force of the spring 53 and holdthe clutch cover 55 in detent fashion against turning on the shaft end57. This construction has been found to more than amply hold the clutchcover 55 from so turning under the action of vibratory forces whicharise during normal tool use. However, when it is desired to adjust thetorque level of the clutch 33, the clutch cover 55 can be turned withthe balls 63, 69 readily camming into and out of successive recesses 67,75. Advantageously, this camming action provides an audible click whichalerts the operator as to the extent of clutch adjustment undergone.

Furthermore, this construction involves a minimum of parts (utilizingthe spring 53 to generate both the clutch frictional force and theadjustment locking force), and minimizes the overall size and costinvolved. The location of the balls 63, 69 in openings in the springcoils renders the detent balls virtually part of the spring 53. Thus,the axial dimension of the clutch 33 is less than it would be were alocking arrangement separate from the spring 53 used. However, the useof the separate balls allows them to be made from a wear resistantmaterial without requiring that the entire spring be so made. Finally,the round configuration of the balls 63, 69 is highly desirable infacilitating ready camming into and out of the recesses 67, 75.

By the foregoing, there has been disclosed a novel slip clutchconstruction calculated to fulfill the inventive objects hereinabove setforth and while a preferred embodiment has been set forth herein,various additions, substitutions, modifi cations, and omissions may bemade thereto.

We claim:

1. In a portable power tool of the type having a tool bit supported forrotation and longitudinal reciprocation, said tool having a transmissionincluding a rotary slip clutch adapted to transmit rotary motion to saidtool bit below a preselected torque level; the improvement in said toolwherein said clutch comprises input and output members, engageable firstand second friction means connected to said input and output members,respectively, a coil spring normally biasing said first and secondfriction means into operative f rictional engagement, ad ustment meansholding said resilient means in its biasing position and movable indirections toward and away from said resilient means to effectadjustment of the biasing force of said resilient means on said firstand second friction means, said coil spring having an opening in one endthereof, and detent means including a ball partially disposed in saidopening and cooperably receivable in recess means in said adjustmentmeans to resist said movement of said adjustment means, whereby thebiasing force of said resilient means inhibits said movement of saidadjustment means.

2. The improvement of claim 1 wherein said ball is constructed ofhardened steel.

3. The improvement as defined in claim 1 wherein said resilient meanscomprises a coil spring, said detent means including at least one ballcarried in each end coil of said spring and cooperable with recess meansin said adjustment means and said first friction means.

3. The improvement of claim 1, wherein said adjustment means includes aclutch cover threaded on said input member.

5. The improvement of claim 1 wherein said ball projects from saidopening from about one-fourth to about one-half the diameter of saidball.

6. The improvement of claim 1 wherein said spring has an opening formedin the other end coil thereof, a ball disposed partially in saidlast-mentioned opening and cooperably receivable in at least one pocketin said first friction means.

7. The improvement of claim 6 wherein said adjustment means and saidfirst friction means each has a plurality of pockets formed therein.

8. A rotary friction clutch comprising generally concentric rotary inputand output members, first and second frictional plate means fixed forrotation with said input and output members, respectively, a compressionspring biasing said first and second friction plate means into operativefrictional engagement, a cage member threaded to said input member andholding said compression spring in biasing relation to said frictionplate means and adapted when threaded along said in ut member to varythe biasing force of said spring on said friction plate means, detentmeans including a ball partially received in an opening formed in oneend coil of said spring, said cage member having at least one pocketadapted to cooperatively receive said ball, whereby to releasably holdsaid cage member against turning movement relative to said input member.

9. A clutch as defined in claim 8 wherein said spring has a ballpartially received in an opening in the other end coil thereof, saidfirst friction plate means having at least one pocket adapted tocooperably receive said last-mentioned ball.

10. A clutch as defined in claim 9 wherein said cage member and saidfirst friction plate means each has a plurality of spaced pocketsadapted to cooperably receive said balls in selected threaded adjustmentposition of said cage member.

11. A clutch as defined in claim 9 wherein said balls are constructed ofhardened steel.

12. A clutch as defined in claim 9 wherein said balls project from saidspring openings from about one-fourth to about onehalf the diameter ofsaid balls.

1. In a portable power tool of the type having a tool bit supported forrotation and longitudinal reciprocation, said tool having a transmissionincluding a rotary slip clutch adapted to transmit rotary motion to saidtool bit below a preselected torque level; the improvement in said toolwherein said clutch comprises input and output members, engageable firstand second friction means connected to said input and output members,respectively, a coil spring normally biasing said first and secondfriction means into operative frictional engagement, adjustment meansholding said resilient means in its biasing position and movable indirections toward and away from said resilient means to effectadjustment of the biasing force of said resilient means on said firstand second friction means, said coil spring having an opening in one endthereof, and detent means including a ball partially disposed in saidopening and cooperably receivable in recess means in said adjustmentmeans to resist said movement of said adjustment means, whereby thebiasing force of said resilient means inhibits said movement of saidadjustment means.
 2. The improvement of claim 1 wherein said ball isconstructed of hardened steel.
 3. The improvement as defined in claim 1wherein said resilient means comprises a coil spring, said detent meansincluding at least one ball carried in each end coil of said spring andcooperable with recess means in said adjustment means and said firstfriction means.
 4. The improvement of claim 1, wherein said adjustmentmeans includes a clutch cover threaded on said input member.
 5. Theimprovement of claim 1 wherein said ball projects from said opening fromabout one-fourth to about one-half the diameter of said ball.
 6. Theimprovement of claim 1 wherein said spring has an opening formed in theother end coil thereof, a ball disposed partially in said last-mentionedopening and cooperably receivable in at least one pocket in said firstfriction means.
 7. The improvement of claim 6 wherein said adjustmentmeans and said first friction means each has a plurality of pocketsformed therein.
 8. A rotary friction clutch comprising generallyconcentric rotary input and output members, first and second frictionalplate means fixed for rotation with said input and output members,respectively, a compression spring biasing said first and secondfriction plate means into operative frictional engagement, a cage memberthreaded to said input member and holding said compression spring inbiasing relation to said friction plate means and adapted when threadedalong said input member to vary the biasing force of said spring on saidfriction plate means, detent means including a ball partially receivedin an opening formed in one end coil of said spring, said cage memberhaving at least one pocket adapted to cooperatively receive said ball,whereby to releasably hold said cage member against turning movementrelative to said input member.
 9. A clutch as defined in claim 8 whereinsaid spring has a ball partially received in an opening in the other endcoil thereof, saId first friction plate means having at least one pocketadapted to cooperably receive said last-mentioned ball.
 10. A clutch asdefined in claim 9 wherein said cage member and said first frictionplate means each has a plurality of spaced pockets adapted to cooperablyreceive said balls in selected threaded adjustment position of said cagemember.
 11. A clutch as defined in claim 9 wherein said balls areconstructed of hardened steel.
 12. A clutch as defined in claim 9wherein said balls project from said spring openings from aboutone-fourth to about one-half the diameter of said balls.